Method for communicating and radio station therefor

ABSTRACT

The present invention relates to method for communicating between a primary station and a secondary station comprising
         (a) at the secondary station, upon arrival of a data packet to be transmitted to the primary station, buffering said data packet in a buffer, and transmitting to the primary station a request for an uplink transmission resource if a request condition is satisfied, said request condition being based on at least one previous grant of uplink transmission resource,   (b) at the primary station, granting to the secondary station an uplink transmission resource to be used.

CLAIM OF PRIORITY

This application is a Continuation of application Ser. No. 12/933,688,filed Sep. 21, 2010, which is a National Stage of InternationalApplication PCT/IB2009/051066, filed Mar. 16, 2009, which claimedforeign priority of EPO 08305065.8 filed Mar. 21, 2008, all of which areincorporated herein in whole by reference.

FIELD OF THE INVENTION

The present invention relates to a method for communicating in anetwork. More specifically, the present invention relates tocommunication between a primary station and a secondary station, in atelecommunication network, like a cellular telecommunication network(e.g. UMTS, GSM).

BACKGROUND OF THE INVENTION

In a cellular network, each cell comprises a primary station, like abase station, or a Node B, or an eNB communicating with a plurality ofsecondary stations, like mobile stations, or User Equipments. To be ableto send data to the primary station on some uplink channels, a secondarystation must have an allocated resource (time slot, frequencysubcarrier, and/or code or likewise).

Many communication systems operate using a centralised scheduler whichis responsible for allocating transmission resources to different nodes.A typical example is the uplink of the UMTS LTE (Long Term Evolution),where the uplink transmissions from different secondary stations arescheduled in time and frequency by the primary station. The primarystation transmits a “scheduling grant” message to a secondary station,indicating a particular time-frequency resource for the secondarystation's transmission, typically around 3 ms after the transmission ofthe grant message. The grant message also typically specifiestransmission parameters as the data rate and/or power to be used for thesecondary station transmission.

In order for the primary station to issue appropriate grants, it needsto have sufficient information about the amount and type of dataawaiting transmission in the buffer of each secondary station.

In LTE, several types of buffer status report (BSR) messages aretherefore defined, which may be transmitted from a secondary station tothe primary station when certain triggers occur. The current version of3GPP TS36.321 is incorporated by reference.

The Buffer Status reporting procedure is used to provide the servingprimary station with information about the amount of data in the uplinkbuffers of the secondary station. Two kinds of Buffer Status Reports areused depending on the events. A short Buffer Status Report (BSR)comprises the identity of a single group of logical channels, togetherwith a 6-bit indicator of the amount of data corresponding to that groupof logical channels currently residing in the secondary station bufferawaiting transmission. A long BSR comprises 4 concatenated short BSRs,each corresponding to a different group of logical channels.

A problem with the BSR procedure defined above is that a secondarystation is only permitted to transmit a BSR if it has a granted resourcein which to transmit. If new data arrives in a secondary station'sbuffer and the secondary station has no granted resource in which totransmit the data or to send a BSR to indicate that it has data awaitingtransmission, the secondary station must either wait until a grant isreceived, or transmit a simpler version of the BSR which can betransmitted using some specially-designated resources which can be usedwithout a specific granted resource. This simpler version of the BSR isknown as a “scheduling request” (SR), and typically comprises only asingle bit to indicate that data is in the buffer. It is also known foran SR to comprise a small plurality of bits, which gives greaterfunctionality. In response to receiving an SR, a primary station mayeither transmit a grant allocating a suitable amount of transmissionresource for the secondary station then to send a BSR, or transmit agrant allocating a larger amount of transmission resource which wouldenable the secondary station to transmit some data in addition to theBSR; however, in the latter case there is typically no means for theprimary station to determine a suitable size of allocation to make,unless the SR comprises more than a single bit.

In a known implementation, a secondary station without an uplinktransmission grant sends an SR as soon as data arrives in its buffer.However, this is inefficient and wasteful of resources if the primarystation would in any case provide a grant within an acceptable delay.

However, if the secondary station were always to refrain fromtransmitting an SR and to wait for a grant to be received, Quality ofService (QoS) criteria could be breached if the primary station did notprovide a grant within an acceptable delay.

SUMMARY OF THE INVENTION

It is an object of the invention to propose a method for communicatingin network which alleviates the above mentioned problem.

Another object of the invention is to propose a method which permits toindicate to the primary station to be aware of the state of the bufferof the secondary stations without creating too much overhead.

Still another object of the invention is to propose a method reducingthe unnecessary transmission of scheduling requests, while allowing QoSrequirements to be satisfied. It is required that uplink datatransmission occurring within specified latency contraints.

To this end, it is proposed a method for communicating between a primarystation and a secondary station comprising

-   -   (a) at the secondary station, upon arrival of a data packet to        be transmitted to the primary station, buffering said data        packet in a buffer, and transmitting to the primary station a        request for an uplink transmission resource if a request        condition is satisfied, said request condition being based on at        least one previous grant of uplink transmission resource,    -   (b) at the primary station, granting to the secondary station an        uplink transmission resource to be used.

As a consequence, this prevents the secondary station from transmittingunnecessary scheduling requests. Indeed, only if an uplink transmissionresource is not received during said time period, the secondary stationsends a scheduling report. Moreover, the time period may be adjusted inaccordance to events or conditions of transmission.

The present invention also relates to a secondary station comprising

-   means for transmitting data to a primary station on an uplink    channel,-   buffering means for buffering data packets to be transmitted to the    primary station upon arrival of said data packets,    -   means for requesting, if a request condition is satisfied, the        primary station to grant an uplink transmission resource, said        request condition being based on at least one previous grant of        uplink transmission resource.

According to another aspect of the invention, a system comprising atleast one secondary station in accordance with the first aspect of theinvention and a primary station, said primary station comprising meansfor granting to the secondary station an uplink transmission resource.

These and other aspects of the invention will be apparent from and willbe elucidated with reference to the embodiments described hereinafter.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will now be described in more detail, by way ofexample, with reference to the accompanying drawing, wherein:

FIG. 1 is a block diagram of a system in accordance with the inventioncomprising a primary station and at least a secondary station.

DETAILED DESCRIPTION OF THE INVENTION

The present invention relates to a method for communicating in anetwork, like a cellular network. For instance, the network may be aUMTS network as depicted on FIG. 1.

Referring to FIG. 1, a radio communication system in accordance with theinvention comprises a primary station (BS) 100 and a plurality ofsecondary stations (MS) 110. The primary station 100 comprises amicrocontroller (μC) 102, transceiver means (Tx/Rx) 104 connected toantenna means 106, power control means (PC) 107 for altering thetransmitted power level, and connection means 108 for connection to thePSTN or other suitable network. Each MS 110 comprises a microcontroller(μC) 112, transceiver means (Tx/Rx) 114 connected to antenna means 116,and power control means (PC) 118 for altering the transmitted powerlevel. Communication from primary station 100 to mobile station 110takes place on a downlink channel, while communication from secondarystation 110 to primary station 100 takes place on an uplink channel.

According to a first embodiment of this invention, it is provided ameans to control the circumstances in which a secondary station sends aScheduling Request (SR) or a request of resource, in order to avoidunnecessary transmission of SRs, while also allowing QoS requirements tobe satisfied (i.e. uplink data transmission occurring within specifiedlatency constraints).

In accordance with this first embodiment of the invention, a secondarystation which does not have an uplink grant may also transmit an SR inresponse to data arriving in its buffer, if the secondary station candetermine that the primary station is not likely to provide a grantwithin an acceptable time delay (and otherwise the secondary stationrefrains from sending an SR or waits for some time duration to elapsebefore sending an SR).

The secondary station sends an SR at the earliest opportunity if thetime since the last grant is greater than a threshold in a first exampleof this embodiment.

In another example of this embodiment, the condition which must besatisfied is that average time between previous grants in a given timewindow is greater than a threshold. This permits to have more equitybetween all the secondary stations.

In another example, the size of resource (measured in e.g. bits)allocated in the previous grant is less than a threshold, or the averagesize of resource allocated in a predetermined number of previous grantsor in all the previous grants received in a given time window is lessthan a threshold. Similarly, the total amount of resource allocated in apredetermined number of previous grants or in all the previous grantsreceived in a given time window is less than a threshold.

In the above examples, the thresholds may be predetermined Thisthreshold may be for example transmitted to the secondary station bymeans of a signaling channel. For instance, the primary station sends ona control channel the time duration of the threshold.

But to obtain a system which is more appropriate to each situation, thethreshold may be dependent on characteristics. In an example of thisembodiment, the threshold depends on one or more data characteristic ofthe data which had arrived in the buffer. Some examples of suitable datacharacteristics include:

-   -   an indication of the priority of the data;    -   QoS parameters of the data (e.g. latency requirements, or a        function thereof)    -   an identity of a logical channel or group of logical channels to        which the data is assigned;    -   the amount of data which had arrived in the buffer;    -   the amount of data in the buffer;    -   the rate of arrival of data in the buffer;    -   the time since the previous arrival of data in the buffer.

Thus, if the data is of high priority, or if the amount of data in thebuffer or the amount of data which had arrived is great, then thethreshold is lower.

In another example, the threshold depends on whether or not a cellchange has occurred within a preceding time period. If a cell change hasoccurred within a preceding time period, the threshold may be lowered.

In still another example, the threshold is based on the time elapsedsince the secondary station last requested a resource by sending an SRor sending a BSR without receiving a corresponding grant. If no resourcehas been allocated to the secondary station for a long time, it may beurgent to provide resource to this secondary station, so the thresholdis lowered to enable the secondary station to request such resource.

In another example of this embodiment, the threshold determinationmethod takes into account one or more characteristics of the radiochannel. Indeed, if the radio channel conditions are not good, it may beinteresting for the secondary station to wait before asking forresource. Examples of radio channel characteristics that can be used tosimply estimate the conditions of the radio channel are given below:

-   -   the rate at which the secondary station could transmit data        under the current channel conditions,    -   the current uplink transmission power requested by the primary        station—e.g. a high power could be an indicator of poor channel        quality;    -   An estimate of the downlink channel channel quality as an        indicator of uplink channel quality (especially in a TDD        system).

A combination of any of the above—e.g. a threshold set on the basis ofpriority of data, but modified according to uplink channel quality—forexample, if the channel quality is good but the UE has not received agrant for a long period, it could be inferred that the absence of agrant is not due to poor channel quality and therefore the threshold forsending an SR could be set lower.

Note that in some embodiments the criteria used to determine whether anSR is transmitted may depend on at least one characteristic of the data,examples of which are:

-   -   an indication of the priority of the data;    -   QoS parameters of the data (e.g. latency requirements, or a        function thereof)    -   an identity of a logical channel or group of logical channels to        which the data is assigned;    -   the amount of data which had arrived in the buffer;    -   the amount of data in the buffer;    -   the rate of arrival of data in the buffer;    -   the time since the previous arrival of data in the buffer.

Note also that an embodiment in which the secondary station sends an SRif the total amount of resource allocated in all the previous grantsreceived in a given time window is less than a threshold, where thethreshold is derived from the amount of data which had arrived in thebuffer, amounts to a situation where the secondary station determinesthat the data which has arrived in the buffer exceeds that which theprimary station has historically expected—in other words, the data whichhas arrived in the buffer is probably outside the knowledge of theprimary station.

A particular example of this embodiment could comprise a configurationin which the primary station configured persistently-scheduled uplinktransmission resources corresponding to a regular arrival rate ofpackets in the secondary station's buffer—for example for a VoIPapplication. If a packet arrived in the secondary station's buffer at adifferent time from one of the usual VoIP time instants corresponding tothe persistent schedule, the secondary station would send an SR, whereasa packet arriving in accordance with the persistent schedule of grantedresources would not trigger an SR.

In another similar embodiment, if a packet arrived in the secondarystation's buffer with a larger size than usual the secondary stationwould send an SR to request additional resources. Whereas a packetarriving with a size in accordance with the persistent schedule ofgranted resources would not trigger an SR.

In one embodiment of this invention, a primary station receives grantsto transmit data from time to time. When a new data packet arrives inthe secondary station's buffer, the secondary station checks thepriority of the data packet, and if the priority is higher than a firstthreshold and the elapsed time since the last received grant is longerthan a second threshold, the secondary station sends an SR; otherwisethe secondary station refrains from sending an SR. The second thresholdmay be a function of the priority—for example, the allowed time delaycould be longer for low-priority data.

In another embodiment of this invention, a secondary station receivesgrants to transmit data from time to time. When a new data packetarrives in the secondary station's buffer, the secondary station checksthe amount of data in the data packet, and if the amount of data ishigher than a first threshold and the elapsed time since the lastreceived grant is longer than a second threshold, the secondary stationsends an SR; otherwise the secondary station refrains from sending anSR. The second threshold may be a function of the amount of data—forexample, the allowed time delay could be longer for small amounts ofdata.

According to another embodiment of the invention, a secondary stationwhich does not have an uplink grant when data arrives in its bufferwaits for a given delay period before it transmits an SR, after a firstSR if any transmitted in accordance with the first embodiment of theinvention . If a grant is received during this period, the secondarystation refrains from transmitting an SR, and uses the transmissionresources provided by the received grant.

In examples of this embodiment, the delay or time period beforetransmitting an SR may be determined according different methods. In afirst variant, this delay is of a predetermined duration. This durationmay be transmitted to the secondary station by means of a signalingchannel. For instance, the primary station sends on a control channelthe time duration.

In another variant, this duration may correspond to one or more datacharacteristic, i.e characteristics of data which had arrived in thebuffer. This permits to have an appropriate time delay to eachsituation. These data characteristics may be for instance:

-   -   an indication of the priority of the data;    -   QoS parameters of the data (e.g. latency requirements, or a        function thereof)    -   an identity of a logical channel or group of logical channels to        which the data is assigned, an identity of a kind of data;    -   the amount of data which had arrived in the buffer;    -   the total amount of data in the buffer;    -   the rate of arrival of data in the buffer;    -   the time since the previous arrival of data in the buffer.

Thus, if the data is of high priority, or if the amount of data in thebuffer or the amount of data which had arrived is great, then the timeduration is shorter.

In another example, the time delay is based on any change of cell. If acell change has occurred within a preceding time period, the time periodduration may be shortened.

In still another example, the time period duration is based on the timeelapsed since the secondary station last requested a resource by sendingan SR or sending a BSR without receiving a corresponding grant. If noresource has been allocated to the secondary station for a long time, itmay be urgent to provide resource to this secondary station, so the timeperiod is shortened.

In another example of this embodiment, the time period duration takesinto account one or more characteristics of the radio channel. Indeed,if the radio channel conditions are not good, it may be interesting forthe secondary station to wait before asking for resource. Examples ofradio channel characteristics that can be used to simply estimate theconditions of the radio channel are given below:

-   -   the rate at which the secondary station could transmit data        under the current channel conditions;    -   the current uplink transmission power requested by the primary        station—e.g. a high power could be an indicator of poor channel        quality;    -   an estimate of the downlink channel quality as an indicator of        uplink channel quality (especially in a TDD system).

In one embodiment of this invention, a secondary station receives grantsto transmit data from time to time. When a new data packet arrives inthe secondary station's buffer, the secondary station checks thepriority of the data packet, and waits for a time period correspondingto the priority of the data packet before sending an SR. For example, ifthe priority of the data is high, the secondary station would wait for ashorter time period than if the priority of the data is low. In anycase, if a grant is received during the time period, the secondarystation refrains from sending an SR.

In another embodiment of this invention, a secondary station receivesgrants to transmit data from time to time. When a new data packetarrives in the secondary station's buffer, the secondary station checksthe amount of data in the data packet, and waits for a time periodcorresponding to the amount of data before sending an SR. For example,if the amount of data is high, the secondary station would wait for ashorter time period than if the amount of data is low. In any case, if agrant is received during the time period, the secondary station refrainsfrom sending an SR.

This invention may be used in communication systems utilizingcentralized scheduling, such as UMTS and LTE, Mobile terminals for usein such systems or Hubs which route calls from multiple terminals tobase stations. Such devices would appear like a UE from the point ofview of the network.

It is to be noted that the present invention is not limited to theexamples described above and can be adapted. For instance, it is to beunderstood that in some adaptations, the role of the primary station maybe a mobile station and the secondary station may be a base station.Other variations to the disclosed embodiments can be understood andeffected by those skilled in the art in practicing the claimedinvention, from a study of the drawings, the disclosure, and theappended claims.

In the claims, the word “comprising” does not exclude other elements orsteps, and the indefinite article “a” or “an” does not exclude aplurality. A single unit may fulfill the functions of several itemsrecited in the claims. The mere fact that certain measures are recitedin mutually different dependent claims does not indicate that acombination of these measured cannot be used to advantage.

1. A method, operable in a processor within a secondary station, saidmethod causing the processor to execute the steps comprising: receivinga data packet containing an amount of data for subsequent transmissionto a primary station; determining whether a grant of uplink resource fortransmission is available at a current time; when said grant of uplinkresource for transmission is not available, determining a time relatingto a previous request for uplink resources for transmission to saidprimary station, determining a difference between said current time andsaid time of a previous request for uplink resources; and transmitting arequest for uplink resources if said difference exceeds a threshold. 2.The method claim 1, wherein said time relating to a previous grant ofuplink resources is an average of times relating to a plurality ofprevious grants of uplink resources.
 3. The method of claim 1, whereinsaid threshold is predetermined.
 4. The method of claim 1, furthercomprising: receiving said threshold from said primary station.
 5. Themethod of claim 1, wherein said threshold is determined based on atleast one characteristic of said received data.
 6. The method of claim1, wherein said threshold is determined based on at least onecharacteristic of a communication channel between the primary stationand the secondary station.
 7. The method of claim 6, wherein saidchannel is one of: an uplink channel and a downlink channel.
 8. Themethod of claim 1, further comprising: when said grant of uplinkresource for transmission is available determining said amount of saidreceived data; determining a size of an available grant of resources;and transmitting a request for uplink resources if said size of saidavailable grant of resources is less than said amount of said receiveddata.
 9. The method of claim 8, wherein said size of an available grantof resources is determined as an average of sizes of a plurality ofprevious grants of uplink resources.
 10. The method of claim 2, whereina number of said plurality of previous grants of uplink resources ispredetermined.
 11. The method of claim 9, wherein a number of saidplurality of previous grants of uplink resources is predetermined.
 12. Amethod operable in a processor in a secondary station, said methodcausing the processor to execute the steps comprising: receiving data;determining an amount of said received data; determining a time since alast grant of resources was received and an amount of said receiveddata; and transmitting a request for resources based on at least one of:said amount of said received data is greater than a first threshold whena grant of resources is available and a time since a last grant ofresources is greater than a second threshold when a grant of resourcesis unavailable.
 13. The method of claim 12, wherein said first andsecond thresholds are determined as one of: respective predeterminedvalues, based on characteristics of said received data, based oncharacteristics of at least one of: uplink channels and downlinkchannels, a time since a last request for resources, and received from aprimary station.
 14. A secondary station comprising: a transceivingsystem; and a processor in communication with a memory, said memoryincluding code, which when accessed by said processor causes saidprocessor to execute the steps of: receiving a data packet containing anamount of data for subsequent transmission to a primary station fromsaid transceiving system; determining whether a grant of uplink resourcefor transmission is available at a current time; when said grant ofuplink resource for transmission is not available, determining a time ofa previous request for uplink resources for transmission to said primarystation, determining a difference between said current time and saidtime of a previous request for uplink resources; and transmitting,through said transceiving system, a request for uplink resources if saiddifference exceeds a threshold.
 15. The secondary station of claim 14,wherein said time of a previous grant of uplink resources is an averagetime of previous grants of uplink resources.
 16. The secondary stationof claim 14, wherein said threshold is predetermined.
 17. The secondarystation of claim 14, further comprising: receiving said threshold fromsaid primary station.
 18. The secondary station of claim 14, whereinsaid threshold is determined based on at least one characteristic ofsaid received data.
 19. The secondary station of claim 14, wherein saidthreshold is determined based on at least one characteristic of acommunication channel between said secondary station and said primarystation.
 20. The secondary station of claim 19, wherein saidcommunication channel is one of: an uplink channel and a downlinkchannel.
 21. The secondary station of claim 14, the processor furtherexecuting the steps: determining said amount of received data;determining a size of an available grant of resources; and transmitting,through said transceiving system, a request for uplink resources if saidsize of said available grant of resources is less than said amount ofreceived data.
 22. The method of claim 21, wherein said size of saidavailable grant of resources is determined as an average of sizes ofprevious grants of resources.
 23. The method of claim 22, wherein anumber of said previous grants of uplink resources is predetermined. 24.The method of claim 22, wherein a previous grants of uplink resources ispredetermined.
 25. A secondary station comprising: a processing system:receiving data; determining an amount of said received data; determininga time since a last grant of resources was received and an amount ofsaid received data; and transmitting a request for resources when saidamount of said received data is greater than a first threshold when agrant of resources is available and a time since a last grant ofresources is greater than a second threshold when a grant of resourcesis unavailable.
 26. A method for communicating between a primary stationand a secondary station comprising: at the secondary station, uponarrival of a data packet to be transmitted to the primary station,buffering said data packet in a buffer, determining whether an uplinktransmission resource is available, transmitting to the primary stationan indication of the amount of data contained in the buffer, determiningwhether a request condition is satisfied, said request condition beingbased on: at least one previous grant of uplink transmission resource;and also the time elapsed since a last transmission of the indication ofthe amount of data contained in the buffer but only when the secondarystation has not received a grant of uplink transmission resource sincethe last transmission of the indication of the amount of data containedin the buffer, transmitting to the primary station a request for anuplink transmission resource if an uplink transmission resource is notavailable and the request condition is satisfied.
 27. The method ofclaim 26, comprising: at the primary station, transmitting to thesecondary station a grant of an uplink transmission resource; at thesecondary station receiving the grant of the uplink transmissionresource, transmitting to the primary station the data packet from inthe buffer of the secondary station after receiving the grant of theuplink transmission resource.
 28. A secondary station comprising meansfor transmitting data and control information to a primary station on anuplink channel, the transmission of data requiring a previous grant ofan uplink transmission resource from the primary station, thetransmission of control information not requiring a previous grant of anuplink transmission resource, the control information including anindication of the amount of data contained in the buffer, bufferingmeans for buffering in a buffer data packets arriving at the secondarystation for transmission to the primary station, means for determiningif an uplink transmission resource is available; means for determiningif a request condition is satisfied, said request condition: being basedon at least one previous grant of a uplink transmission resource; andalso being based on the time elapsed since a previous transmission tothe primary station of an indication of the amount of data contained inthe buffer but only when the secondary station has not received a grantof uplink transmission resource since the last transmission of theindication of the amount of data contained in the buffer, means forrequesting, the primary station to grant an uplink transmissionresource, when an uplink transmission resource is not available and therequest condition is satisfied.
 29. The secondary station of claim 28,wherein the satisfaction of the request condition depends on the timeelapsed since the last grant of resource being greater than a threshold.30. The secondary station of claim 28, wherein the satisfaction of therequest condition depends on quantity of uplink transmission resourceallocated in the previous grant of the uplink transmission resourcebeing less than a threshold.
 31. The secondary station of claim 28,wherein the satisfaction of the request condition depends on the averageamount of resource allocated in a set of previous grants of uplinktransmission resource being less than a threshold.
 32. The secondarystation of claim 28, wherein the satisfaction of the request conditiondepends on the total amount of resource allocated in a set of previousgrants of uplink transmission resource being less than a threshold. 33.The secondary station of claim 29, wherein the threshold depends atleast on at least one of a set of data characteristics of a data packetin the buffer.
 34. The secondary station of claim 33, wherein the set ofdata characteristics of a data packet in the buffer comprises at leastone of the following: indication of data priority; Quality of Serviceparameters; identity of a logical channel or group of logical channelsto which the data packets are assigned; the amount of data in the bufferof the secondary station; the amount of data which arrived at thesecondary station; a rate of arrival of data at the secondary station;and/or the time elapsed since a previous arrival of data.
 35. Thesecondary station of claim 29, wherein the secondary station operates ina radio cell, and wherein the threshold is based on the time elapsedsince the secondary station has started to operate in said radio cell.36. The secondary station of claim 29, wherein the threshold depends atleast on the time elapsed since the secondary station last transmitted arequest for an uplink transmission resource.
 37. The secondary stationof claim 29, wherein the threshold depends at least on the time elapsedsince the secondary station last transmitted a request for an uplinktransmission resource corresponding to a specific amount of data and didnot receive a corresponding grant of resource.
 38. The secondary stationof claim 29, wherein the threshold depends at least on a set of uplinkchannel characteristics.
 39. The secondary station of claim 38, whereinthe set of uplink channel characteristics comprises at least one of thefollowing: the uplink channel quality, a transmission rate correspondingto the uplink channel quality, the uplink transmission power.
 40. Thesecondary station of claim 38, wherein the set of uplink channelcharacteristics is estimated based on characteristics related to adownlink channel.